Thursday, July 02, 2009

What gene studies reveal about the diversity and resilience of mind, and the limitations of psychiatric disease classification

This research further confirms results first published in Science three months ago. The continued blurring of the diagnostic boundaries between manic-depression and schizophrenia is significant, as is the relationship to control of the immune system. It has always been interesting to contemplate similarities between the immune and nervous systems …

Scientists have identified thousands of tiny genetic variations which together could account for more than a third of the inherited risk of schizophrenia…

… The findings came from work by three separate teams, who analysed DNA from thousands of people.

The studies - the biggest ever into the genetics of schizophrenia - appear in the journal Nature.

The findings suggest that schizophrenia is much more complex than previously thought, and can arise not only from rare genetic variants, but common ones as well…

… The researchers say that individually many of the genetic variations they have identified play only a tiny role in raising the risk of passing schizophrenia down the generations … "Cumulatively, they play a major role, accounting for at least one-third - and probably much more - of disease risk."

All three studies highlight genes found on Chromosome 6 in area known as the Major Histocompatibility Complex, which plays a role in the immune system, and in controlling when other genes are switched on and off.

The researchers believe this might help explain why environmental factors also seem to affect risk for schizophrenia…. For example, there is evidence that children whose mothers contract flu while pregnant have a higher risk.

In total the researchers identified 30,000 tiny genetic variants more common in people with schizophrenia.

A similar pattern was found in people with bipolar disorder…

… Dr Thomas Insel, of the US National Institute of Mental Health, said: "These new results recommend a fresh look at our diagnostic categories.

… "If some of the same genetic risks underlie schizophrenia and bipolar disorder, perhaps these disorders originate from some common vulnerability in brain development." …

… Sabine Bahn, who led the research, published in The Lancet, said: "We believe that our results provide strong evidence for oligodendrocyte and myelin dysfunction in schizophrenia and bipolar disorder.

"The high degree of correlation between the expression changes in schizophrenia and bipolar disorder provide compelling evidence for common pathophysiological pathways that may govern the disease phenotypes of schizophrenia and bipolar disorder." …

In particular childhood onset “bipolar disorder” seems to have a great deal in common with early onset schizophrenia.

In a more abstract direction this research provides some tantalizing hints about the diversity of mind/brain, and the emergent resilience of the brain/mind. Thousands of gene variants all affecting minds in unpredictable ways.

By comparison we can see the diversity of our bodies, but they’re really all somewhat familiar. From a distance a parade of human forms is not that interesting. Four feet to seven feet tall, a bit of pigment variation, some muscular variability – but really, not so different. Dogs are much more diverse.